Tool wear incurred in machining operations which results in production part size variation requires adjustment in tool position which has been accomplished in various ways. Tool holders in the form of cartridges rigidly mounted with provision for deflection of a cutting insert by a central drawbar acting on a ramp surface are commonly employed for such purpose, particularly in the case of boring tools where the drawbar is reciprocated to relax deflection for withdrawal of the cutting point free of part contact and oppositely actuated to register with an adjustable stop to deflect the tool point to its effective cutting position.
In such systems, automatic part size gaging coupled to means for effecting drawbar stop adjustment have been effectively used in order to maintain part size uniformity over production runs within the capacity of the tool point between sharpening or replacement intervals. A typical system of this type is disclosed in U.S. Pat. No. 3,740,161 issued Jun. 19, 1973.
As an alternative to ramp surface displacement for deflecting adjustment of the tool point, a rigidly mounted tool, such as at the end of a boring bar, may be adjusted through radial or angular deflection of the entire boring bar at its mounting base; again, automatic gaging coupled with means for effecting such deflection, has been employed to maintain part size uniformity through wear compensation means. A typical system of this type is disclosed in U.S. Pat. No. 3,753,624 issued Aug. 21, 1973.
While such systems are adapted to generate adjustment of the tool point automatically, verification of the proper adjustment in conventional practice is not established until successive parts are gaged following the adjustment. Such open loop adjustment leaves uncertainty as to whether a proper adjustment has been made; for example, if the adjustment involves a stepper motor which does not move, or a microscrew for stop adjustment is bound up, or a piston assembly for retracting a drawbar fails to retract and seat on an adjusted microscrew stop.